Guides to numbers and verification codes
Straight answers to the questions that come up around verification texts: why a code doesn’t arrive, what kind of number an app will accept, what is safe, and how software and AI agents can receive a code.
Choosing a number
How long to rent a numberMatch a day, a week, a month or a year to how long the account will text you.
Buying a non-VoIP numberSix things to check before paying for a non-VoIP number, and how ours answers each.
One-time number or rentalWhen one code from one app is enough, and when you need the number for longer.
Receive SMS on a computerForward texts from your own phone, or use a number whose texts appear in a browser.
A second number for verificationA second SIM, a calling app or a receive-only rental: which one your codes actually need.
A US number from abroadThe routes to a US number from another country, and what each one needs.
When an app won’t take a number or the code doesn’t come
“Cannot be used for verification”What the message means, the refusals like it at other apps, and what to try in order.
Verification code not receivedThe three common reasons a code doesn’t arrive, and what to do about each, in order.
Which apps accept virtual numbersWhat 16 apps’ own help centers say about VoIP and other kinds of numbers, row by row.
Why apps reject VoIP numbersThe line-type check behind VoIP refusals, the reasons apps give, and what non-VoIP does and doesn’t change.
Staying safe
Are free receive-SMS sites safe?Who can read a code sent to a free public number, and what they can do with it.
A temporary number for 2FAMostly no: why, what to use instead, and the one case where a rented number is reasonable.
When a temporary number expiresWhy someone else can get your codes after a number ends, and what to change before it does.
For developers and AI agents
AI agent SMS verificationThe four ways an agent can receive a verification code, and what each one needs.
Browser agent phone verificationGive a browser agent a tool that gets a number and returns the code, over MCP or from your own code.
Give Claude a phone numberSet up Claude, Claude Code or Cursor to receive a verification text, step by step.
SMS MCP serverThe MCP server’s reference: endpoint, tools, sign-in, access levels and spending limits.
Temporary phone number APIThree REST calls from an API key to a verification code, with the limits that apply.
Testing SMS OTP end to endA Playwright test and a Cypress task that read your app’s sign-up code from a real text.